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Topic: Time to Troubleshoot the furnace

Posted By: zach477 on 10/02/15 03:34pm

My Atwood furnace worked great when I tested it before buying the coach...

I haven't tried to use it since then, but now that it's getting chilly I tried to fire it up, but the blower won't come on.

As I turn the thermostat up, I hear a "click" from the furnace, and I can see a green LED on the furnace circuit baord come on. So no error codes, and since it seems to be triggering the furnace to "come on", I'm assuming the thermostat is working. Correct?

I'm thinking its a problem with the blower. I have a multimeter, and have read some trouble shooting guides, but I don't think I have QUITE enough information to continue troubleshooting. For instance, when it says "check that the furnace has 12 volts". How? Which wired do I test?

Any other troubleshooting tips?

Thanks


Posted By: donn0128 on 10/02/15 03:37pm

Propane?
12VDC?
Demand?
Those are the three things you need to have to have heat!






Posted By: Toddupton on 10/02/15 03:38pm

Bee hive in the blower maybe. They love the smell of gas. Do you have any screens on the outside intake or vent?


Posted By: Tin Pusher on 10/02/15 03:45pm

Nothing gonna happen til the blower runs....


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Posted By: Old-Biscuit on 10/02/15 03:57pm

DC Voltage comes from a 'fused' circuit at DC Dist. Panel
Goes to:
t-stat and to an ON/OFF switch (local on frame of furnace).
From ON/OFF switch it goes to circuit board...that is ahy you have a GREEN light. Board has power.

From t-stat it goes to:
limit switch and sail switch where it stops until fan comes on and makes u sail switch
it also goes to circuit board for the 'timed delay' function (starts fan which makes up sail switch allowing voltage to go back to board....time delay then allows voltage to gas valve & sparker)

Sounds like issue is with timed delay circuit on board or with 4 wire connector on board.

When T-stat makes up (CLICK) DC voltage should be on:
RED wire from board to fan motor
BLUE wire in 4 wire connector to board
WHITE/BLUE (could be either) wire from t-stat to limit switch/to sail switch (but not on white wire from sail switch to 4 wire connector until fan runs)

* This post was edited 10/02/15 04:19pm by Old-Biscuit *


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Posted By: zach477 on 10/02/15 04:05pm

donn0128 wrote:

Propane?
12VDC?
Demand?
Those are the three things you need to have to have heat!


I have propane, but that doesn't matter since it won't try to light until after the blower starts.

My batteries and converter are brand new, fully charged, and I'm plugged in. I don't know how to test if the furnace is getting 12v.

It's cool enough that there should be demand. Especially since when I tested it, it was a mid summer morning. It's colder than that right now.


Posted By: westend on 10/02/15 04:06pm

Chris Bryant, a member of this Forum has libraries of appliance owners and service manuals for download on his Website. The service manuals for furnaces have a trouble shooting chart and descriptions of the locations for electrical diagnosing.
Thanks Chris!!

BTW, the blower needs to operate before the gas valve will open. There is a sail switch that interrupts current to the gas valve. If the sail switch doesn't move or close--no gas to igniter and burner.


'03 F-250 4x4 CC
'71 Starcraft Wanderstar -- The Cowboy/Hilton


Posted By: zach477 on 10/02/15 04:09pm

Toddupton wrote:

Bee hive in the blower maybe. They love the smell of gas. Do you have any screens on the outside intake or vent?


Looking into the exhaust pipe, I don't see any obstructions. I can also reach in and turn the fan with my finger, and it doesn't feel like it's obstructed either.

I want to put my multimeter to good use, but I don't know what wires to be testing.


Posted By: Old-Biscuit on 10/02/15 04:18pm

westend wrote:

Chris Bryant, a member of this Forum has libraries of appliance owners and service manuals for download on his Website. The service manuals for furnaces have a trouble shooting chart and descriptions of the locations for electrical diagnosing.
Thanks Chris!!

BTW, the blower needs to operate before the gas valve will open. There is a sail switch that interrupts current to the gas valve. If the sail switch doesn't move or close--no gas to igniter and burner.


FAN is NOT coming on...........so issue is with power to fan motor or circuit board

Should be something like this wiring scheme

[image]


Posted By: zach477 on 10/02/15 04:28pm

westend wrote:

Chris Bryant, a member of this Forum has libraries of appliance owners and service manuals for download on his Website. The service manuals for furnaces have a trouble shooting chart and descriptions of the locations for electrical diagnosing.
Thanks Chris!!

BTW, the blower needs to operate before the gas valve will open. There is a sail switch that interrupts current to the gas valve. If the sail switch doesn't move or close--no gas to igniter and burner.


Yes, I have read that, but it for a novice like me, it's not enough info. For example, it says to check the voltage at the furnace. Great, but it does't tell me how. :/


Posted By: zach477 on 10/02/15 04:31pm

Old-Biscuit wrote:

westend wrote:

Chris Bryant, a member of this Forum has libraries of appliance owners and service manuals for download on his Website. The service manuals for furnaces have a trouble shooting chart and descriptions of the locations for electrical diagnosing.
Thanks Chris!!

BTW, the blower needs to operate before the gas valve will open. There is a sail switch that interrupts current to the gas valve. If the sail switch doesn't move or close--no gas to igniter and burner.


FAN is NOT coming on...........so issue is with power to fan motor or circuit board

Should be something like this wiring scheme

[image]


Ok, so what wires do I test?


Posted By: Toddupton on 10/02/15 04:57pm

Red and black at the motor or from the board red and ground.


Posted By: MEXICOWANDERER on 10/02/15 05:04pm

Oooooooo lookie, a circuit breaker. A circuit breaker connected to ALWAYS GOT POWER 12-volts. RED

And then YELLOW for negative. GROUND.

Waddles, and got feathers, check both sides of the circuit breaker and see if it quacks [emoticon]

Not joking. Rap the side of the blower motor with a hammer HANDLE.


Posted By: zach477 on 10/02/15 05:51pm

Ok so I'm getting proper voltage to the circuit breaker, but the blower is not getting any voltage.

It's dark on now, so I had to close it up for the night, but what's my next step?


Posted By: enblethen on 10/02/15 06:48pm

Remove cover from the thermostat. connect the two furnace wires together. The furnace should start the fan and produce heat. Separate the wires and furnace should go into cool down mode.
If this happens the thermostat is the problem.
Did you check for on off switch on thermostat.


Bud
USAF Retired
Pace Arrow

2003 Chev Ice Road Tracker



Posted By: zach477 on 10/02/15 07:39pm

enblethen wrote:

Remove cover from the thermostat. connect the two furnace wires together. The furnace should start the fan and produce heat. Separate the wires and furnace should go into cool down mode.
If this happens the thermostat is the problem.
Did you check for on off switch on thermostat.


Do you mean the control panel? Or the little thermometer on the wall?

Also, I have two temperature sensors, but I don't have different zones on the control panel so I'm not sure why there are two? Could one be for AC and one for the furnace?

* This post was edited 10/02/15 07:45pm by zach477 *


Posted By: enblethen on 10/02/15 08:03pm

The small wall unit.
Small on about two inches square
What is make of other temperature sensors?


Posted By: zach477 on 10/02/15 08:10pm

enblethen wrote:

The small wall unit.
Small on about two inches square
What is make of other temperature sensors?


Well the control panel is and Intellitec ECC2. I don't know the make of the sensors. It doesn't say on them.

I'm not sure that the thermostat is the problem, though. When I set it to "Heat", and turn the temperature dial up, I hear a click, and a green led on the furnace circuit board turns on. So it seems to be telling the furnace to turn on.


Posted By: enblethen on 10/02/15 08:17pm

You can do the same thing at the furnace. Two wire in unit commonly blue. Connect a jumper there.
Your light on furnace would indicate that it is getting signal from the thermostat. Try spinning the fan with power shut off to see if it spins freely.
Model of furnace?
Is there a small circuit breaker on the fan housing? Should have white or red button to reset.


Posted By: zach477 on 10/02/15 08:28pm

enblethen wrote:

You can do the same thing at the furnace. Two wire in unit commonly blue. Connect a jumper there.
Your light on furnace would indicate that it is getting signal from the thermostat. Try spinning the fan with power shut off to see if it spins freely.
Model of furnace?
Is there a small circuit breaker on the fan housing? Should have white or red button to reset.


Right, so if it's getting signal, its not the thermostat.

The fan spins freely when I use my hands.

When measuring voltage to the fan, there is none.

It's an Atwood 8535-IV

It has a Circuit breaker, and I have tried resetting it multiple times.


Posted By: Old-Biscuit on 10/02/15 08:44pm

zach477 wrote:

enblethen wrote:

You can do the same thing at the furnace. Two wire in unit commonly blue. Connect a jumper there.
Your light on furnace would indicate that it is getting signal from the thermostat. Try spinning the fan with power shut off to see if it spins freely.
Model of furnace?
Is there a small circuit breaker on the fan housing? Should have white or red button to reset.


Right, so if it's getting signal, its not the thermostat.

The fan spins freely when I use my hands.

When measuring voltage to the fan, there is none.

It's an Atwood 8535-IV

It has a Circuit breaker, and I have tried resetting it multiple times.

As I poster earlier....
Wouldn't have GREEN light (power on) if it was the ON/OFF switch.

Problem is either with 4 wire connector on board or the timed delay function circuit on board.

BLUE wire in 4 wire connector should be hot when t-stat makes up (CLICK). So board is not getting that power thru BLUE wire (bad connector/dirty contacts etc.) OR board is bad.

* This post was edited 10/02/15 08:52pm by Old-Biscuit *


Posted By: westend on 10/02/15 10:19pm

I'd suggest to bypass the circuit breaker, manually. If you remove the two wires from the circuit breaker, set your thermostat, wait for the green light then touch the wires together to make contact. If the blower turns, the problem is the circuit breaker. If no blower turning, the problem is probably the fan motor.

If you are able to power the blower by bypassing the circuit breaker, don't run it like that. Replace the breaker with a better one. There is a reason the breaker failed and if it's because of a fault in the motor, you don't want a bigger problem to fix.


Posted By: Chum lee on 10/02/15 11:06pm

Zack: A shot in the dark. When my Atwwood 8500 series furnace fan wouldn't run and the burner wouldn't light, it first became a little flaky meaning over 6 months time it would work . . not work, . . . . work, . . not work, then not work at all. No fan, no heat no nothing. I took off the exterior cover and found that the ground connection {black wire to yellow wire) at the multi point connector where the coach power connects to the heater box melted/fried/failed. The black (10 gage) wire from the coach was fine but the yellow (14 gage) ground wire inside the heater box was fried for about 4 inches. I replaced all the yellow internal ground wires with new 10 gage wire. Now it works fine. Some engineer at Atwood decided that a 10 gage to 14 gage ground connection would be fine. It wasn't. DC power flows from negative to positive. I suspect that all Atwood furnaces wired from the factory this way will eventually fail. Mine is a low time 1999 model. Look inside your heater box. If the multi point connector is melted or fried, you may have this problem too. It's not in the troubleshooting guide.

The wiring diagram is in the manual which is helpful. Some one else already gave you the link.

Chum lee

* This post was edited 10/03/15 06:32am by Chum lee *


Posted By: zach477 on 10/02/15 11:57pm

Chum lee wrote:

Zack: A shot in the dark. When my Atwwood 8500 series furnace wouldn't light, it first became a little flaky meaning over 6 months time it would work . . not work, . . . . work, . . not work, then not work at all. No fan, no heat no nothing, I took off the exterior cover and found that the ground connection {black wire to yellow wire) at the multi point connector where the coach power connects to the heater box melted/fried/failed. The black (10 gage) wire from the coach was fine but the yellow (14 gage) ground wire inside the heater box was fried for about 4 inches. I replaced all the yellow internal ground wires with new 10 gage wire. Now it works fine. Some engineer at Atwood decided that a 10 gage to 14 gage ground connection would be fine. It wasn't. DC power flows from negative to positive. I suspect that all Atwood furnaces wired from the factory this way will eventually fail. Mine is a low time 1999 model. Look inside your heater box. If the multi point connector is melted or fried, you may have this problem too. It's not in the troubleshooting guide.

The wiring diagram is in the manual which is helpful. Some one else already gave you the link.

Chum lee


I'll check this out tomorrow, but what exactly do you mean by "heater box"? Are you just talking about taking the cover off of the outside of the RV? Or actually taking apart the furnace?

Thanks


Posted By: Chum lee on 10/03/15 06:17am

The heater box is the galvanized sheet metal enclosure that houses the blower motor, the heat exchanger/burner can and all the electric wiring/circuitry for the furnace. The thermostat is separate. The supply ducts come out of the box on the interior of your MH. If your furnace is mounted horizontally, remove the exterior cover ((4 screws secure it. Its the cover with the air intake/exhaust on it) the multi point house connector penetrates the sheet metal enclosure on the left side in the upper 1/3 of the box. I hope you have small hands. If the yellow ground wire is burned you'll see it right away. If the ground connection is bad inside the multi point terminal, you'll have to separate the multi point connector to see that. I can email you a pic of mine if you can't locate what I am talking about. No need to take apart the furnace other than remove the outside cover for this fix.

Chum lee


Posted By: enblethen on 10/03/15 08:10am

You will need to check for voltage. Check the circuit breaker to insure it has power coming in and then output to the motor.


Posted By: Chris Bryant on 10/03/15 08:25am

zach477 wrote:

My Atwood furnace worked great when I tested it before buying the coach...

As I turn the thermostat up, I hear a "click" from the furnace, and I can see a green LED on the furnace circuit baord come on. So no error codes, and since it seems to be triggering the furnace to "come on", I'm assuming the thermostat is working. Correct?

Thanks


My info says that a solid LED on that board means internal board failure- the only Atwood board I know of with an LED is a fan control board, and my chart give error codes for solid on , 1 flash, 2 flash, and 3 flash- they are all errors.


-- Chris Bryant


Posted By: enblethen on 10/03/15 08:34am

Chris: I have been waiting for you to respond.
OP: Does your circuit board look similar to this one from Dinosaur?
Dinosaur Fan-50


Posted By: turbojimmy on 10/03/15 09:18am

enblethen wrote:

You will need to check for voltage. Check the circuit breaker to insure it has power coming in and then output to the motor.


I was thinking the same thing, but the diagram - if it applies to his unit - shows the breaker protecting the whole shootin' match. BAsed on the diagram, there wouldn't be a green light on the board if that breaker was bad.

Even so, I'd bypass the breaker and/or check for voltage on the other side of it.


1984 Allegro M-31 (Dead Metal)




Posted By: zach477 on 10/03/15 03:11pm

Chris Bryant wrote:

zach477 wrote:

My Atwood furnace worked great when I tested it before buying the coach...

As I turn the thermostat up, I hear a "click" from the furnace, and I can see a green LED on the furnace circuit baord come on. So no error codes, and since it seems to be triggering the furnace to "come on", I'm assuming the thermostat is working. Correct?

Thanks


My info says that a solid LED on that board means internal board failure- the only Atwood board I know of with an LED is a fan control board, and my chart give error codes for solid on , 1 flash, 2 flash, and 3 flash- they are all errors.



I was under the impression that it was a red LED that indicated an error. Mine is green. That's still an error?

Also, I just noticed that it is a DInosaur board. Does that mean its an aftermarket circuit board or would that come stock?


Posted By: Old-Biscuit on 10/03/15 03:35pm

Dinosaur Board..........(YES different then OEM)

1) IF fan doesn't come on AND GREEN Light is ON then 'sail switch' is stuck closed.
(Must be open before fan runs and closes it)

2) Fan runs and GREEN light does NOT come on then problem with 'sail switch/high limit switch' circuit......either sail switch is not closing or high limit is stuck closed.

You have a stuck closed sail switch....issue #1


Posted By: Bird Freak on 10/03/15 04:16pm

dinosaur is aftermarket but a very good one.


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Posted By: Chris Bryant on 10/03/15 04:32pm

A solid green on a Dinosaur means the sail switch is stuck closed- it's attached to the plastic blower cover, inside. The board knows it should not get power through the sail switch if the blower is not energized, so it doesn't start.

From the directions at http://dinosaurelectronics.com/Instructions/Fan50PP_inst.pdf
Quote:

IF!? For some reason the fan does not come on and the GREEN LED is lit on the
circuit board, the sail switch is stuck in the closed position. The Fan 50 Plus Pins
is designed to stop and do nothing if the sail switch is stuck closed.



Posted By: zach477 on 10/03/15 06:02pm

Chris Bryant wrote:

A solid green on a Dinosaur means the sail switch is stuck closed- it's attached to the plastic blower cover, inside. The board knows it should not get power through the sail switch if the blower is not energized, so it doesn't start.

From the directions at http://dinosaurelectronics.com/Instructions/Fan50PP_inst.pdf
Quote:

IF!? For some reason the fan does not come on and the GREEN LED is lit on the
circuit board, the sail switch is stuck in the closed position. The Fan 50 Plus Pins
is designed to stop and do nothing if the sail switch is stuck closed.


Nice! I'm glad we got that figured out!

Seems like something fairly easy to fix? Or will it just get stuck again next time?


Posted By: enblethen on 10/03/15 06:58pm

The furnace is one of those maintenance items. Blowing it out at least start of each season will keep debris away from the sail switch. You can use a can of compressed air or a nozzle on your air compressor if you have one.
A vacuum will do a partial job, but the compressed air seems to work better for me.
Chris has been a great help for many people on this site.
Thanks Chris for all you do!


Posted By: Dick A on 10/03/15 11:06pm

If the sail switch is the problem I would suggest replacing it and perhaps the igniter. They are inexpensive and easy to do at the same time while the unit is open.


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Posted By: zach477 on 10/06/15 04:33pm

Well it rained for a couple of days straight, and now its 85 degrees out, so I haven't had a chance/need to dive into the furnace, but when I do I'll post the results. [emoticon]


Posted By: zach477 on 10/17/15 11:29am

Ok now that it is getting chilly out and I have some time to look at it....

In order to get at the sail switch, will I need to disconnect the propane line?


Posted By: zach477 on 10/18/15 03:09pm

UPDATE: I got it working again. Before taking it apart, I gave it a few solid smacks on the top of the fan. It release the sail switch and now we're good to go. [emoticon]


Posted By: mchero on 10/20/15 02:31pm

Not a bad idea to pull the furnace and give it a good cleaning on a work bench. Not hard to pull, just make sure you locate the screws holding it down.

I had a 93 Pace Arrow Diesel pusher with two Hydro-Flame furnaces. One was burning strange so I pulled it & found a partially rusted burner. Also found an old mouse nest in one of the ducts!
The sail switch on the Hydroflames was simply a veeder type microswitch with a long arm & small square or "sail". Hard to imagine the actual switch going out BUT mud daubers & such love to bild mini mud mansions in those furnaces. Also, the squirrel cage blowers get dirty & out of balance.
Sometimes I read threads about people who oil the blower motors because they squeak but then report back that the squeaking starts up again! The blower motors themselves run around 100 bucks.
Those Hydroflame furnaces are practically bulletproof "IF" you keep them clean and maintained. Everything, including ignitor boards in that 93 Pace was original and 100% functioning because it was maintained. Sold her last year and do indeed miss her!


Robert McHenry
Currently, Henniker NH
07 Fleetwood Discovery 39V
1K Solar
2005 Jeep Grand Cherokee
Prior:1993 Pace Arrow 37' Diesel


Posted By: wolfe10 on 10/20/15 03:40pm

If you do pull it to clean (a good idea), PLEASE be sure to replace the gaskets. Gaskets in good shape (won't be after you take the furnace apart) are critical for keeping Carbon Monoxide out of the inside.


Brett Wolfe
Ex: 2003 Alpine 38'FDDS
Ex: 1997 Safari 35'
Ex: 1993 Foretravel U240

Diesel RV Club:http://www.dieselrvclub.org/


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